By Melinda T. Willis

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The inoculations will help boost the ability to control a potential smallpox terrorist attack by preparing rapid response teams that can be sent at the first signs of an outbreak.

Officials announced the vaccinations Sunday.

Stretching Current Vaccine Supply

But for the millions of people in the United States who could be at risk from any smallpox outbreak — a consistent fear of those considering possible biological attacks — there is not yet enough vaccine to go around.

Researchers have been testing whether diluted doses of existing smallpox vaccine can work.

Meanwhile, U.S. health officials say it will take considerable time to create enough new full-strength doses to otherwise meet possible demand.

"I think we have pushed this system as much as we can," James LeDuc, acting director of the Division of Viral and Rickettsial Diseases at the National Center for Infectious Diseases, told a Senate subcommittee on Bioterrorism Preparedness and Smallpox Research today.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said officials hope to produce and deliver 250 million doses of vaccine to the federal government by the end of 2002 as part of an intermediate plan.

The long-term goals include developing a new generation of smallpox vaccines that could be given to all citizens, from those with compromised immune systems to pregnant women.

Buying Time

The news of the time frame came as the first shot was administered Friday afternoon to test subjects in a National Institutes of Health study of more than 650 participants to determine the effectiveness of diluted doses of existing vaccine.

In the event of a terrorist attack with smallpox, diluted vaccine could be used until new vaccine can be produced.

"This is a kind of stop-gap measure pending additional manufacture of new vaccine," says Dr. Robert Belshey, director of the Center of Vaccine Development at St. Louis University.

The trial dose of diluted vaccine was administered at St. Louis University. The University of Maryland Center for Vaccine Development, the University of Rochester School of Medicine and Baylor College of Medicine begin administering the vaccine today. The study is scheduled to last 2 1/2 months.

Diluted Vaccine

Last year, St. Louis University researchers conducted a pilot study with 60 participants and found that 70 percent of subjects responded to a one in 10 dilution of the vaccine.

According to Belshey, the current trial will compare the response to undiluted vaccine to the one in 10 dilution as well as to a one in five dilution.

Additionally, that 30 percent of subjects who did not respond to the one in 10 dilution will get another dose one week later.

"If we get another 70 percent response in that group of people, that will give us a total of over 90 percent," says Belshey.

Therefore, if effective, dilution may stretch the existing supply of smallpox vaccine, currently estimated at 15 million doses, to 75 million doses.
 

ABCNEWS' Lynne Adrine contributed to this report